Rotary mercury jet high speed switch



Feb. 25, 1964 H. NATHAN ROTARY MERCURY JET HIGH SPEED SWITCH Original Filed June 2?, 1955 V Fig. I

2 Sheets-Sheet 1 Fig. 4

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Feb. 25, 1964 H. NATHAN 3,122,614

ROTARY MERCURY JET HIGH SPEED SWITCH Original Filed June 27, 1955 2 Sheets-Sheet 2 7 Fig. 2-

22 I... flayww a IN VEN TOR. HAROLD (NM/l NA THAN tional heat and rough surfaces.

7 base of the switch into a reservoir within the rotor.

United States Patent O 3,122,614 ROTARY MERCURY JET HIGH SPEED SWITCH Harold Nathan, 7%0 Alvarado, La Mesa, Calif. Continuation of application Ser. No. 518,421, June 27, 1955. This application Nov. 5, 1959, Ser. No. 851,201

' 2i (Claims. (Cl. 200- 32) (Granted under Title 35, US). Code-(1952), sec. 266) This invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the pay ment of any royalties thereon or therefor.

This application is a continuation of now-abandoned application, Serial No. 518, 421, filed June 27, 1955, for Rotary Mercury Jet High Speed Switch.

This invention relates to rotary switches and more particularly to an improved rotary mercury jet high speed multiple contact switch capable of switching in excess of 14,400 samples per second at a rotating shaft speed of 3600 rpm.

Heretofore mechanical and electronic switches have been used for high speed switching. However, mechanical switches use brushes or metal to metal contact, resulting in varying contact resistance due to inertia, fric- They are noisy in operation, need constant service because of wear and are limited as to contact time. The vacuum tube method of high speed switching requires a large number of complex circuits and the linearity for tubes in comparable switch circuits and mixers must be identical, creating a problem in design and maintenance. The mercury switch of this invention overcomes these disadvantages by'using a jet stream of mercury to bridge between the rotor and contacts and therefore is self-adjusting. With no frictional contacts, it is noiseless and hasvery low contact resistance. It has a high current-carrying capacity, a long trouble free life and no warm up period is required as in the case of electronic switches. It requires only a fraction of the power required by electronic switches of comparable capabilities.

The switches illustrative of the present invention may be used in telemetering, sonar scanning, switching in connection with a time-shared display scope where a large number of targets or other information is to be displayed on a single CRT, and in other applications requiring a compact, high speed, single or multiple pole sequential sampling switch. i

In the mercury switch of this invention, a spinning rotor scoops up mercury from a mercury pool contained in the base of the switch and directs this scooped-up mercury in a series of streams which enable an electrically-conductive mercury path to be established between a first group of stationary contact pins joined to a common external electrical lead and, on a sequential time sharing basis, successive pins of a second stationary group of contact pins which may connect to individual external electrical leads I or be joined together in any desired combinations. The rotor scoops the mercury from a pool of mercury in the This spinning reservoir serves as the source of the mercury streams which enable mercury bridging between the contact pin groups.

In one embodiment the spinning rotor has at least one jet feeder arm, continually fed from the reservoir, which sprays, through a nozzle at its outer end, a jet stream of mercury which sequentially strikes, as said rotor spins, successive contact pins, representing the second group, which are peripherally spaced beyond the rotational path of the feeder arm nozzle. Submerged in the mercury 7 pool at the base of the switch is the first group of contact diametrically opposite each other on the rotor.

3,122,614 Patented Feb. 25, 1964 "ice cury in the reservoir and the mercury in the base a series of uninterrupted mercury streams are directed from the reseivoir, via ports therein, to join the pool of mercury in the base of the switch. The result is the formation of a continuous, uninterrupted electrical path between the two groups of contact pins, part of which is a moving mercury bridge which enables sequential electrical joinder of successive contact pins of the second group to the first group of pins.

In another embodiment, at least two circumferentially spaced operative feeder arms are employed, generally Here the contact pins of both groups are located peripherally beyond the locus of movement of their respective feeder arm nozzles so that successive pins of each group sequentially become targets of the jet streams issuing from the respective spinning feeder arms. In this embodiment the electrically-conductive mercury paths between the groups of pins is defined by the issuing jet streams in union with the mercury path through the coupling reservoir.

Very significant to the invention is the nature and placement of the contact targets engaged by the mercury jet stream. The 'cylindrically-shaped contact pins, preferably of the smallest possible diameter able to withstand the stream impact without material vibration, used herein, permit a predictability of switching times not available with the bulky contact targets previously used in such switches. Prior use of flat-faced contact members is disadvantageous in that the mercury tends to ricochettherefrom so as to interrupt the jet stream causing discontinuity of this impinging stream. Presentment of a fiat surface to the impinging jet stream also is undesirable because the mercury stream on hitting a fiat surface has a tendency to spread out in an irregular splash formation before ricocheting. This splash causes unpredictable leading and inherent difliculty leading to unpredictability of On inherent difiiculty leading to unpredictability of the On and Oif times is the nature of the jet stream itself; the sides of the stream are turbulent to a considerable degree so that any on or Otf time dependent upon contact of the side of the jet stream with a contact member is relatively unpredictable. The contact pins used herein with their small cross-sections approach knife edges in their affect upon the stream and, in conjunction with their relative spacing, yield maximum dispersionof the richochetecl mercury in such direction as to present the'minimum amount of disruptive interference by the ricocheted droplets with the continuing jet stream (as previously noted) and a predictability of impact by the stream previously unobtained. This predictability of impact is, of course, abetted by the non-interference with the stream by the random, ricocheted droplets, but to a large extent it is due to the fact that contact time herein is not dependent upon the erratic side of the stream but upon the front of the jet stream which is relatively stable. The close spacing of adjacent cylindrical contact pins enables the contacting stream to be shaped by the previous contact pin so that a blunt, constant front face of the formed stream, not the turbulent edge of the stream, determines contact time. The sharply-roughened non-wetting surface of the target contact pins employed herein presents a target to the jet stream which is susceptible to being wiped clean, by the force of the stream, of the scum and oxides that build up on the target contact pins and which present troublesome impedance to the flow of electrical current; this same surface characteristic makes for easy dispersion of the gaseous cushion which serves to impede the jet stream path to the contact pin. The optimum placement of the contact pin targets so as to be parallel to the axis of the rotor minimizes a change in operating characteristic One feature of the invention is the structure for scooping-up and carrying the mercury from the switch base to the reservoir. Rotating annular scoops disposed at the bottom of the rotor continually pass over a series of pits located in the base wherein mercury spherules continually rise up into the path of the scoops to have their upper portions plowed off and carried by the spinning rotor into the reservoir. This form of pick-up avoids the disadvantage of other types of mercury pick-up where the side portions of the spinning rotor come into dynamic contact with the supplied mercury to exert a rotary and outward thrust upon it. Where the mercury sits within a container such as the switch bowl this thrust by the rotor produces a radially oscillating movement of the mercury which ends in erratic pick-up of the mercury and imbalance of the rotor. This scoop pick-up of the mercury provides for pick-up even when the switch is severely tilted from the vertical or when the switch is run at excessively high speeds.

Another feature of the invention is the rotor reservoir with its overflow ports and return stream ports. At the slowest operating speed of the rotor, there is suflicient pick-up of mercury by the scoops to keep the reservoir full beyond the overflow level. At a faster rotary speed the additional mercury picked up is passed off through the overflow ports. In eflect, then, the operating amount of mercury in the reservoir is isolated from changes in mercury pick-up due to changes in rotational speed of the switch or other causes such as tilting, for example. The issuing jet stream coming from the constant-level reservoir consequently is pressure-regulated to avoid the undesirable change in stream angle which would be characteristic of previous fluid switches not having this pressure regulation. This maintaining of the constant mercury level in the reservoir, furthermore, makes for a more balanced rotor. in previous switches not having the overflow ports an increase in mercury pick-up would not only give undesirable changes in issuing jet stream characteristic due to erratic mercury pressures in the rotor, but also would result in the dumping of the excess mercury, unable to be handled by the rotor, back down the mercury intake path so that the overflow would, in effect, fight the input. In addition to causing erratic pick-up this produces another untoward result. This intake path overflow passes out the bottom of the rotor to be reflected from the switching chamber back to the rotor. The result is a disruptive pe iodic friction drag on the rotor caused by a fast-moving object (the rotor) meeting a slow-moving surface (the reflected mercury).

The overflow ports also provide a means for removal of scum from the mercury in the rotor since the scum which floats on the upper surface of the mercury will be carried oil in the overflow stream. This obviates a continual problem in mercury switches for scum, if allowed to accumulate in the rotor without removal, will ultimately gather and impede the flow of mercury through the nozzle orifice(s) The scum removal feature in this rotor leads to a longer operation before servicing.

The return stream ports, applicable to the first-mentioned switch embodiment, which lead from the reservoir at a point beneath the surface level of the mercury therein, direct uninterrupted continuous streams from the reservoir to the pool of mercury in the base to ensure electrical continuity between the mercury pool in the base and the mercury in the reservoir. This is necessary because the scooped-up mercury enters the reservoir in an interrupted stream not suitable for maintaining electrical continuity. The combination of the reservoir and the return stream ports enables the switch to continue operation during sudden intervals of extreme tilting of the switch from its vertical position.

A further feature of the present invention is the nature of the conducting path through the switch. Between the different groups of contact pins which represent the switch terminals the conducting path herein is all mercury. This is in contradistinction to previous mercury switches which employ the rotor as part of the conducting path. 11 such switches utilizing the rotor as part of the conducting path a main difiiculty is due to the resistance built up between dissimilar metals. Between the metal rotor and the mercury, which represent dissimilar metals, oxides are built up which bring into being resistance in the conducting path. The resulting resistive coatings due to these oxides are accumulative, continually affecting the operating characteristics of the switch. In this switch the target contact pins, subjected to the cleansing action of the jet stream, are relatively immune to resistive coating and where base contact pins are employed they are maintained submerged under the surface of the mercury in the switch base to keep the possibility of resistive coating formation thereon to a minimum. These base contact pins may be made of precious or semi-precious metals as a further effort in this direction. Thus the conducting path herein substantially avoids the dissimilar metal resistance which characterizes those prior switches using the rotor as a portion of the conducting path.

Another important feature of the present invention is the self-cleaning and impurity separating action which gives it a long, trouble-free life requiring only a 1,000 hour check-over by non-technical personnel, usually consisting of merely draining and refilling with clean filtered mercury. For this purpose the scum removal from the reservoir is supplemented by a series of mercury impurity traps. The fluid system in the switch is a closed one, the mercury coming from the reservoir ports and nozzle(s) being returned to the annular scoops for pick-up and recryoling; the impurity traps are disposed in the return paths of impurity-laden mercury coming from the target contact pins and from the overfiowports.

For multiple-pole switching the required number of switch housings and rotors are stacked in coaxial banks, each switching chamber being self contained and having no electrical contact with any other chamber. The target contact pins of each chamber may be rotated relative to one another to provide any relative phase characteristics desired. The rotors for the various switching chambers are fixedly mounted on a single, common motordriven shaft. This single, common shaft arrangement produces a switch superior to those where the individual shafts of each switching chamber are coupled together. Phase angle differences are relatively critical herein and, when mechanical coupling is present, mechanical creepage and give in the mechanical couplings prevent the various switching chambers from being properly locked in phase. Use of the single shaft also reduces the number of bearings required.

It is an object of this invention to provide an improved mercury switch.

Another object is the provision of a high speed mercury switch.

Still another object is to provide a mercury switch suitable to a wide range of speeds.

Another object is the provision of a mercury switch which will operate at angles of tilt up to 45 from its normal vertical position.

A further object is to provide a mercury switch ensures a continuous, uninterrupted electrically-conductive mercury path between the input and output conections to the switch.

An additional object is to provide a mercury switch wherein resistance in the electrically-conductive path is reduced to a minimum.

Another object is to provide a mercury switch having a self-cleaning and impurity-separating action which ensures a long period of trouble-free operation and a minimum requirement for maintenance and repair.

Still another object is to provide a light weight switch presenting a minimum of alignment and balance problems.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein: f

FIG. 1 is a vertical cross-:section-al view of the switch;

FIG. 2 is a plan view of the switch base;

FIG. 3 is a vertical sectional view along the line TEL-ill of FIG. 2 showing the various mercury streams; and

MG. 4 is a partial vertical sectional view of a modified embodiment. I

Referring now to the drawing wherein like numerals designate like parts throughout the several views, there is shown in FTG. l a cross-sectional View of the switch mounted and secured to'the shaft 11 of a synchronous motor 12. The embodiment shown has three identical rotors and housings in stacked relationship although it should be understood that more or less maybe used, de-

pending upon the number of switches and contacts desired. The contact-pin-bearing covers 37 may be rotationally adjusted relative to one another to establish the phasing relationship desired. Around the periphery of the rotor 13 stationary contact pins 14 are mounted on the cover 37 of the chamber parallel to the axis of the rotor. The side walls 16 and base 17 of the chamber are sloped and baffled. The base of the chamber con ,tains two concentric mercury-bearing rings 18, 19. Mercury flows from ring 18 to ring 1 through aseries of circumferentially spaced routes, each route being defined by feeder hole inlet 21, feeder hole 20, and restrictor hole 36. To establish electrical connection with the mercury in the base 1'7 base contact pins 15 are installed in the feeder holes 2% and extend beyond feeder hole inlets 21; these base contact pins 15 have external terminals contactor ring 19 through three contactor ports 27 to provide continual electrical. connection between the mercury inside the rotor and that in the pools in the chamber base 17.

The rotor 13 has two hollow arms so constructed that mercury from the rotor reservoir 24 flows into them. One arm '28 is merely a counterbalance. The other arm, the feeder or rotor ejection arm 29 has one or more ejection holes (pin contactor ports). When the rotor 13 turns, the reservoir 24 and the feeder arm 29 fill with mercury and a small stream of mercury is thrownfrom the feeder arm toward the stationary contact pins 14. Thus, a circuit is closed when the stream impinges on the metalic surface of a contact pin 14 and opened when the stream passes by a pin 14 on its way around the periphery.

Each pole of the multiple-pole switch can be adjusted for operation and locked in relation to other poles for synchronization.

The rotor assembly, preferably of non-conducting material such as plastic, has been constructed of four pieces; pickup scoop 23, two arms 28, 29, and that portion containing reservoir 24. These pieces are joined together into an integral unit not intended for disassembly, However, the rotor may be made of two, pieces, the arms becoming integral with the reservoir body. The rotor has the following functions: it picks up mercury, maintains a supply of mercury in its reservoir, removes scum from its inside by means of overflow ejection, maintains electrical contact with the mercury at the base. of the chamber,

d and ejects a stream of mercury onto the stationary switch contact pins. 7

Scoop 23 provides a practical lift for the mercury and works consistently over a wide range of speed. Its operation is satisfactory even when the quantity of mercury fed to it is varied by tilting the switch. Two teeth are used on the scoop to help counterbalance the rotor during operation. A number of downwardly-pitched grooves or feeding slots 32 are cut in the base 17 of the chamber to run from pool contactor ring 19 through the annular wall 30, which separates pick-up area 33 from contactor ring 19, downwardly into pick-up area 33. The inboard ends of these slots 32, asbest seenin FIG. 3, form pits under the locus of movement of scoop 23. Mercury flows from contactor ring 19 down these slots 32 to continually form, in the pits, globules 25 whichrise into the path of the teeth of scoop 23 to be caught up by the teeth and carried into rotor reservoir 24. If the rotating rotor were allowed to strike the mercury flowing toward the scoop, the mercury would acquire a circular motion around and away from the rotor, resulting in poor annular portion referred to as cup lip'34. Since reservoir 24 is kept spinning and the mercury therein is ac cording'ly carried to the radially outer portion of reservoir 24 by the centrifugal action thereon, cup lip 34 might be looked upon as the top edge of the centrifugally orientedmercury bearing vessel defined by reservoir 24. Each of the teeth 23a of pick-up scoop 23 is formed with .an upwardly curving mercury bearing and deflecting path as seen for example at 23b in FIG. 1.

Mercury picked up in the pick-up area by a scoop tooth 23a will be carried upwardly and directed outwardly into reservoir 24 by such mercury bearing and deflecting path 23b which (leads directly into the reservoir 24 proper. It is by such I pick-up and transport by scoop 23 that the mercury is carried over cup lip 34 and into reservoir 24-. An ample supply of mercury should always be carried in the reservoir because all electrical conducting paths through the rotor are mercury to mercury. The reservoir capacity should also be suflicient to allow switch operation during periods of intermittent mercury pickup as a result. of tilting the switch. Rotor 13 is constructed with overflow outlets 26 at the top inside edge of its reservoir 24. These overflow outlets maintain a uniform pressure on the rotor orifice due to the mercury in the reservoir by draining off all mercury inside the reservoir that exceeds the edge of the overflow outlets. Since scum and impurities float toward the inner surface of the mercury as it is carried in the reservoir 24, the major portion of the scum inside the rotor is removed along with the reservoir overflow. At the slowest operating speed of the rotor there is suflicient pick-up of mercury by scoop 23 to maintain overflow from reservoir 24 so that the -mercury entering the rotor will continue to sweep the scum off the inner surface of the mercury in the reservoir. The overflow holes 26remove all the excess mercury; no mercury is ejected over the rotor cup lip 34.

As illustrated by FIG. 3, three types of mercury streams are continually flowing during normal operation of the rotor: (A) overflow, (B) mercury-pool-contactor streams, and (C) switch-pin-contactor stream. The overflow streams (A) from the four outlets 26 should eject some mercury most of the time to ensure proper scum elimination and to indicate that the reservoir is filled to capacity.

The overflow is not part of any electrical circuit, soit may be of an interrupted nature. The overflow capacity of the rotor must dispose of all excess mercury. This excess is at a maximum when all four feeder holes 20 in the base are supplying mercury to the pick-up area 33 during a vertical switch position. This is done by making the diameter of outlets 26 larger than the restricter holes 36 which feed the pool contactor ring 19 and pickup area 33. The outlets of the four overflow holes have a downward angle of approximately 45 and eject the mercury down into the overflow area 18 of the chamber.

The meroury-pool-contactor streams (B) maintain an electrical circuit between the mercury in the base 17 of the chamber and that in the rotor reservoir 24. The pool contactors 27 are fed from the outside edge of the rotor reservoir 24, and they continue to spray mercury streams during switch-tilting periods. The streams have a downward trajectory toward the pool contactor ring 19 in the chamber base. The mercury pool contactors 27 consist of three spaced holes, to ensure electrical continuity at a speed of 1800 r.p.m. and higher. 'Fewer than three holes should not be used, as the mercury ring formed in the mercury pool contactor area may not be continuous because of tilting or jarring of the switch in operation.

The pin-contactor stream (C) flows from the outside tip of the feeder arm 29. It sequentially makes electrical contact between the rotor 13 (as it rotates) and the stationary contact pins 14-. The stream may be composed of more than one jet of mercury, all fed by the same feeder arm, to give the stream more contact width. The orifice of the switch-pin-contactor port 31 may be round or slotted, and the stream flows either horizontally or downward at angles to 45, depending on the angle of the jet aperture. An optimum orientation is to have the target portions of the contact pins 14 parallel to the axis of the rotor and the jet stream issuing from port 31 so as to be perpendicular to the target portions of the contact pins.

The feeder arm 29 supplies mercury from the rotor reservoir 24 to the switch-pin-contactor ports 31 set in its outer tip. The feeder arm, in normal operation, is always full of mercury which is part of the electrical circuit of the switch. A counterbalance arm 23 is used to offset the weight of the feeder arm 29' and thereby balance the rotor. The spaces for mercury in the counterblance arm and in the feeder arm are equal. The leading edges of the rotor arms are designed to deflect downward any random particles of mercury with which they come in contact.

The chamber is formed by the switch housing which consists of a base 17 and a cover 37, both of which are non-conducting and preferably of plastic. The cover 37 serves as a holder for the contact pins 14 set around the periphery of the rotor 13, and the base keeps the rotor supplied with mercury. A motor shaft 11 penetrates the chamber. To make a simple assembly for multiple-pole switching, the cover of the lower pole may be combined with the base of the upper pole, in an integral unit to be molded of a the-rmosetting plastic. A number of such housings could be stacked on top of each other, thereby forming the required number of chambers. An individual base or cover could be made by cutting off the unwanted portion of the housing.

A collar 38 surrounds the motor-shaft opening in the base of the chamber in order to retain mercury. The shoulder of the collar must be higher than the top level of the mercury carried in the chamber. The collar is not a bearing for the rotor shaft, nor does the rotor pickup scoop 23 ride on it. The shoulder on the collar coupled with the shoulder on the inside of the pickup scoop has been an effective barrier to any mercury going down the shaft opening, in spite of agitation ofthe mercury by' the pickup scoop 23. The pickup area 33 for the rotor scoop 23 surrounds the retainer collar 38 in the base of the chamber (FIG. 2). The four feeding slots 3:2v supply it with mercury from the pool contactor ring 19'. Recessed feeding slots are used to keep the mercury from touching the rotor and moving away from the scoop thereby improving the efiiciency of the rotor pickup. The pool contactor ring 19* (FIG. 2) is located around the pickup area 33. it is recessed below the outer top edge or" the feeding slots 32 and supplies them with mercury. The rotor 13 constantly sprays a number of streams of mercury into the pool contactor ring 19. The rotation of these streams tends to keep the mercury rotating in the contactor ring 19. The outer edge of the cont-actor ring 19 is serrated at 39 to reduce this tendency, but no attempt is made to halt the mercury completely because some rotation helps maintain a ring of mercury during tilting. However, because of the multiple streams of the rotor, it is not essential to maintain a complete ring at all times. The pool contactor ring 19- is supplied with mercury through the restrictor holes 36 from the feeder holes 20. The pool contactor ring 19 is separated from the overflow area 18 by a flange 41. The basic function of the feeder hole inlets 21 and feeder holes 20 in the base .17 of the housing is to supply mercury from the overflow area 18 to the scoop pickup area 33 via contactor ring 19. The restrictor holes 3 6 govern the quantity of mercury which passes. The quantity is also influenced by the degree of rotation of the mercury in the pool contactor ring 19. The feeder hole inlets 21 tap the mercury in the chamber overflow ring 18 at a point above its base and below the operating level of mercury in ring 1 8 to prevent scum recycling through the rotor. Agitation of the mercury in the overflow area 18 by the rotor overflow stream (A) helps prevent scum entering the feeder hole inlets 21. The feeder holes 21 in the base extend to the outside of the switch housing and are plugged by the terminal ends of base contact pins 15. A single feeder hole should supply enough mercury for continuous operation. Four symmetrically arranged feeder holes 20 are used to allow for tilting. The base contact pins 15 are inserted through the feeder holes 20. These base pins 15 extend into the flow region of each hole to ensure contact with the mercury. The outer perimeters of both the base 17 and the cover 37 of the chamber are baflied to control recocheting of the mercury ejected by the rotor. Bafiled run-off slots 42 extend from the outer edge of the base to the overflow ring 18.

The spaced stationary contact pins 14 are secured to the cover 37 of the housing. They act as a target for the mercury stream ejected by the rotating rotor arm 29. While the number of target contact pins 14 is dependent upon the size of the switch, with a 3" diameter rotor rotating at a shaft speed of 3600 r.p.m., as many as 240 pins have been used successfully. The contact pins 14 are placed so that the pin contact or target area intercepts only an unbroken, undistorted portion of the mercury stream. This undistorted portion is the tip of the stream formed by the previous contact and therefore the pins should be spaced as closely as possible so that the tip of the stream formed by the previous pin will strike the next pin. As only the tip of the stream gives a consistent On time, the edges of the stream should not be used when consistent switching is desired.

The contact pins 14 must be as small as possible to reduce splatter and reception of stray mercury particles, yet they must be large enough to maintain their necesessary physical strength. The contact stream must also be very small so as to break up into droplets as quickly as possible. For example, 240 contact pins composed of .014" wire have been set in a diameter of 3". This represents a contact spacing of approximately .039" and allows a gap of .025". This is scanned by a rotor at 3600 rpm. When a jet orifice of .004" hole diameter was used, there is a definite make and break between each contact pin 14, with an Off time of approximately 10% of the On time. This represents 14,400 contacts per second. With a jet orifice of .006", there is no break between adjacent contact pins (there is a bridging of adjacent pins by the jet stream), necessitating leaving one pin unconnected where Otf time is desired. This Off time is determined by jet orifice size and can be as small as of On time even with the pin unconnected. Electrical continuity may be established in sequential order by connecting alternate pins, for example, to provide a common terminal.

More than one jet stream may impinge the pins from the same reservoir. This multiplies the scanning rate by the number of streams to obtain faster scanning without increasing the rotational speed.

Etching or finely sand-blasting the target contact pins 14 helps the mercury jet stream to make and maintain contact with these pins. A film coating of scum and oxide tends to build up on the contact surfaces. In addition, gas pressure in butter-like fashion tends to form between the contact surfaces and the oncoming jet stream. The sharply-roughened surface (produced by mechanical or chemical means) of the target contact pins 14 enables the jet stream to easily penetrate the film coating and, moreover, makes for easier diffusion of the gas barrier, yielding the establishment of good contact by the jet stream with these target contact pins 14. The cylindrical configuration of the pins also aids in the dispersion of the gas barrier since it gives the bulk of the intervening gas an easy escape route.

The start of the On and Off times of the switch are more predictable and consistent as the gap between the rotor arm and contact pin 14 is reduced. Also the wiping or cleaning action of the stream is more noticeable. However, a contact pin too close to the nozzle orifice interferes with the normal flow of the stream and produces a slight burble eifect. The minimum distance between the orifice and contact pins for nozzle orifices of 0.010 inch and less is approximately /52 inch.

The target contact pins 14 are the nonwetting type; i.e., they are made of a metal that does not become wet or form an amalgam with mercury. Examples of such metals are Inconel or stainless steel. Mercury does not normally cling to this type of surface. This type of pin has decided advantages for high-speed switch design in that the switch-pin target dimension presented to the mercury stream never varies. A switch with such pins has a long life. Magnification of the impact surface on versions of this type of pin does not reveal wear or deterioration at the end of 1000, hours of continuous operation. The force of the mercury stream should be great enough to wipe off scum accumulation from the impact area of the pin; the wiping action may also be influenced by the size of the mercury stream and the direction of the jet in relation to the direction of rotor rotation.

In another embodiment multiple operational feeder arms may be used to electrically connect, through the mercury jetstreams issuing from the feeder arms and the intermediate reservoir mercury, the various contact pins sequentially engaged by the respective streams. FIG. 4 illustrates such an embodiment showing operational arms 43 and 44 situated for connecting contact pins which are 180 apart. This embodiment also differs from the previous-noted one in that the base contact pins 15 are missing and along with them contactor ports 2'7 which are required only when base'contact pins are present. Pin 14 represents one group of'pins and pin 14' represents the opposing group pin with which it is electically connected by the mercury fiuid. In this FIG. 4 embodiment a mercury jet stream will issue from each of the respective feeder arms 43 and 44. As the issuing jet stream of mercury from feeder arm 43 strikes a contact pin herein designated with the numeral 14, the jet stream from the oppositely-disposed feeder arm 44- will strike an oppositely disposed contact pin 14'. In an exemplary embodiment half of the contact pins mounted in the contact-pin-bearing cover 37 will be connected to a common external electrical lead (i.e., connected in parallel) and the other half of the contact pins will be individually connected to separate external electrical leads. Pins 14' here are in operative effect equivalent to the base contact pins 15 of the FIG. 1 embodiment. Looking (in plan view) at the conventional circular config ration of the various contact pins it can be seen that,

in this circular configuration, contact pins 14 (which are to be individually connected to separate external leads) form a semicircle and pins 14' (which are to be connected in parallel to a common external lead) form the other half of the total circular configuration formed by all the various contact pins. In this embodiment both groups of contactpins, connecting to the input and output circuits, respectively, are subjected to the cleansing action of jet stream impacts.

The drawing shows the switch with the exception of metal contact pins 14 and 15 and metal shaft 11 as being formed of nonconductive plastic. Thisconstruction ensures a minimizing of the difiiculty produced by resistance built up in areas of contact between dissimilar metals. When a high degree of material strength is desired in the rotor 13 it may be formed of metal, thus striking a compromise between greater strength of the rotor and the presence of some dissimilar metal resistance introduced thereby.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be tuiderstood that it is intended to cover all changes and modifications of the disclosed invention which do not constitute departures from the spirit and scope of this invention. 7

What is claimed is: p 1. A fluid switch comprising a plurality of contact pins, some of said contact pins comprising a parallelconnected first group adapted to connect to a common external electrical lead and the. balance of said contact pins comprising a second group adapted to individually connect to separate external electrical leads, a body of electrically-conductive fluid, means for establishing a substantially scumsfree continuous uninterrupted bridge I of said electrically-conductive fluid between contact pins of said first group and successive pins of said second group and electrically-nonconductive means for supporting and positioning said plurality of contact pins, housing said fluid-bridge-establishing means, filtering scumand other impurities from said electrically-conductive fluid, and supplying saidelectrically-conductive fluid to said withsaid axis; siad'rotor including a pair of circumferentially-spaced nozzles at its outer'portion, one of said nozzles beingdirected toward contact pins of said first group at the time that the other of said nozzles is directed toward contact pins of said second group throughout the rotation of said rotor, a common fluid reservoir locatcdinboard of said nozzles, conduit means connecting said reservoir to each of said nozzles for permitting centrifugally-actuated passage of fluid into each of said nozzles for issuance therefrom, as said rotor rotates, of a jet stream which successively engages the pins in the respective circuit sections, excess overflow means leading from said reservoir for maintaining a constant fluid level in said reservoir and for separating scum and other impurities from the fluid in said reservoir and pumping means at the lower portion of said rotor actuated by the rotation of said rotor for ll pumping into said reservoir fluid supplied to said fluidbridge-forming means.

4. A fluid switch comprising a container having upwardly-extending sides and a bottom portion adapted to accommodate an electrically-conductive fluid; a body of electrically-conductive fluid contained in said bottom portion; a plurality of freely spaced contact pins mounted within said container and located above said fluid-accommodating bottom portion, said pins being electrically insulated from one another and each of said pins having an output terminal adapted to connect to an individual external electrical lead; electrically-conductive means passing through said container for establishing electrical communication between said fluid in saidbottom portion and an external circuit means; and power-driven means disposed within said container for maintaining a moving bridge of said conductive fluid running from said body of fluid in said bottom portion strike, in the form of a jet stream, each of said contact pins in succession; the portion of each said contact pins in the region or" contact with said jet stream defining a jet stream target portion, said jet stream target portions of successive of said contact pins defining spaces therebetween which are free of any intervening structure which might serve as lodgment surfaces for the conductive fluid or which would impede free dispersal of the conductive fluid after it has operatively engaged a given contact pin.

5. The switch of claim 4 wherein the jet stream target portions of said contact pins are small-diametered cylinders so as to approach knife edges in their eflect upon the stream without being susceptible to material vibration such as would characterize conventional knifeedge structure.

6. The switch of claim 5 wherein said contact pins are made of nonwetting metal.

7. The switch of claim 5 wherein the jet stream target portions of said contact pins are spaced closely to one another so that each previous contact pin enables the following contact pin to be first struck, not by the turbulent side of the jet stream, but by a blunt stable forward poriton of the jet stream formed by the previous contact pin.

8. The switch of claim 4 wherein said contact pins have sharply-roughened surfaces.

9. The switch of claim 4 wherein said power-driven means comprises a rotor means, said rotor means consisting of pumping means for pumping fluid from said body of fluid in said bottom portion and conduit means connected to said pumping means for conveying said pumped fluid, freeing said pumped fluid of scum, directing said pumped fluid in a pressure-regulated jet stream at substantially constant pressure into successive engagement with said contact pins as said rotor means rotates and maintaining uninterrupted fluid continuity between said body of fluid in said bottom portion and said jet stream enga ing said contact pins.

10. The switch of claim 9 wherein the portion of each contact pin engageable by said jet stream is disposed parallel to the axis of said rotor means.

11. The switch of claim 9 wherein said pumping means comprises at least one annular scoop disposed at the bottom of said rotor means for scooping up conductive fluid from said body of fluid in said bottom portion and pumping said fluid into said conduit means as said rotor means rotates.

12. The switch of claim 9 wherein said conduit means comprises a reservoir leading from said pumping means, overflow outlet means leading from said reservoir and terminally directed toward the bottom portion of said con tainer for spilling over excess fluid from said reservoir so as both to maintain a constant operating level of fluid in said reservoir and to carry off scum from the fluid in said reservoir, port means leading from said reservoir for directing a continuous, uninterrupted fluid-stream from the fluid in said reservoir to the fluid in said bottom portion so as to maintain electrical continuity between the fluid in said bottom portion and the fluid in said reservoir, nozzle means at the outer portion of said rotor means for directing said fluid jet stream into successive engagement with said contact pins as said rotor means rotates and passage means interconnecting said reservoir and said nozzle means for providing a path for said fluid from said reservoir to said nozzle means, said overflow outlet means providing a fluid path separate from the path said fluid takes as it passes from said pumping means into said reservoir.

13. The switch of claim 12 wherein said overflow outlet means leads from an inner radial position in said reservoir and wherein said uninterrupted-fluid-stream port means leaves said reservoir from a position therein which is located radially outwardly of the place of departure from said reservoir of said overflow outlet means so that the fluid streams passing through said port means to said bottom portion leave said reservoir at a point below the scum-bearing surface level of the fluid in said reservoir whereby said streams are scum free.

14. The switch of claim 4 wherein said bottom portion comprises means for combining the fluid expended against said contact pins with the fluid streams proceeding from said port means and from said overflow outlet means and conveying the combined body of fluid to said annular scoop for transmission of said fluid to said conduit means and means in the path of the fluid coming from said contact pins and from said overflow outlet means for filtering out scum and other impurities in said fluid.

15. A mercury supply and pick-up device comprising a power-driven rotor having conduit means, at least one annularly-disposed scoop at the bottom of said rotor, said scoop being adapted to lead into the conduit means of said rotor, container means for maintaining a supply of mercury in position suitable for pick-up by said scoop, said container means comprising a pick-up area immediately beneath said scoop, the outer limits of said pick-up area being substantially defined by the projection of the locus of the outer portion of said scoop on said container means as said rotor rotates, a mercury supply well located outboard of said pick-up area, the inner wall of said supply well serving as a barrier for preventing mercury in said supply well from passing into said pick-up area, and at least one downwardly-sloping channel passing from said supply well through said inner wall into said pick-up area, the inboard end of said channel forming a pit located directly under the path of movement of said scoop, said pit serving as a build-up area wherein mercury passing down said channel continually forms a globule which rises into the path of said scoop to have its upper portion caught up by said scoop and conveyed into the conduit means of said rotor.

16. A rotary switch comprising a plurality of coaxial banks of electrically-conductive contact pins adapted to individually connect to separate external electrical leads, the contact pins of the respective banks forming concentric configurations about said common axis, a body of electrically-conductive fluid individual to each bank, a sole common one piece continuous power-driven shaft passing through said banks along said axis, means individual to each bank fixedly mounted on said common shaft for maintaining a continuous, moving bridge of conductive fluid, drawn from the body of conductive fluid of the bank, between said body of fluid and successive pins of said bank, electrically-nonconductive means for supporting each of said banks of pins in a rotationally shiftable manner about said common axis, for separately housing the fiuid-bridge-forming means of each bank, for supporting each body of conductive fluid, for supplying fluid from each of said fluid bodies to its fluid-bridgeforming means and for returning to each body of fluid the fluid expended against the contact pins of the bank by its fluid-bridge, and electrically-conductive means individual to each bank for establishing electrical connection between each of said bodies of fluid and external circuit means.-

17. A fluid switch comprising a container having upwardly-extending sides and a bottom portion adapted to accommodate an electrically-conductive fluid; a body of electrically-conductive fluid contained in said bottom portion; a plurality of spaced contactpins mounted within said container with a free air gap around each pin and located above said fluid-accommodating bottom portion, said pins being electrically insulated from one another and each of said pins having an output terminal adapted to connect to an individual external electrical lead; electrically-conductive means passing through said container for establishing electrical communication between said fluid in said bottom portion and an external circuit means; and power-driven means disposed within said container for maintaining a moving bridge of said conductive fluid running from said body of fluid in said bottom portion to strike, in the form of a jet stream, each of said contact pins in succession; the free air gap around each of said contact pins making for maximum dispersal in a direction away from the operative jet stream of conductive fluid ricocheted from said contact pins and further negating the presence of lodged conductive fluid particles in contact with said contact pins, said lodged conductive fluid particles being a source of erratic make, said free air gaps break contacts and further allowing for the easy dispersal of gases which would impede the operative transit to said contact pins by said jet stream.

18. A high speed fluid switch comprising a plurality of contact pins, some of said contact pins comprising a parallel-connected first group adapted to connect to a common external electrical lead and the balance of said contact pins comprising a second group adapted to in dividually connect to separate external electrical leads, a body of electrically-conductive fluid, means for establishing a continuous uninterrupted bridge of said electricallyconductive fluid between contact pins of said first group and successive pins of said second group and electricallynonconductive means for supporting and positioning said plurality of contact pins, housing said fluid-bridge-establishing means, and supplying said electrically-conductive fluid to said fluid-bridge-forming means.

19; The switch of claim 4 wherein the jet stream target portions of said contact pins are small-diameter cylinders having sharply-roughened surfaces.

20. The switch of claim 1 wherein the operative electrically-conductive-fluid-contacting portions of said contact pins are cylindrical in shape, small in diameter and have sharply-roughened surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 688,068 Cunningham Dec. 3, 1901 866,289 Luschka Sept. 17, 1907 1,136,058 Sperry Apr. 20, 1915 1,181,711 Wilson May 2, 1916 2,438,067 Luhn Mar. 16, 1948 2,444,687 Widakowich July 6, 1948 2,609,461 Holcomb et al. Sept. 2, 1952 2,782,273 Davis et a1. Feb. 19, 1957 FOREIGN PATENTS 130,537 Great Britain Aug. 7, 1919 384,241 Germany Oct. 30, 1923 

1. A FLUID SWITCH COMPRISING A PLURALITY OF CONTACT PINS, SOME OF SAID CONTACT PINS COMPRISING A PARALLELCONNECTED FIRST GROUP ADAPTED TO CONNECT TO A COMMON EXTERNAL ELECTRICAL LEAD AND THE BALANCE OF SAID CONTACT PINS CONPRISING A SECOND GROUP ADAPTED TO INDIVIDUALLY CONNECT TO SEPARATE EXTERNAL ELECTRICAL LEADS, A BODY OF ELECTRICALLY-CONDUCTIVE FLUID, MEANS FOR ESTABLISHING A SUBSTANTIALLY SCUM-FREE CONTINUOUS UNINTERRUPTED BRIDGE OF SAID ELECTRICALLY-CONDUCTIVE FLUID BETWEEN CONTACT PINS 